Safety device



S. R. BROWN March 4, 1930.

SAFETY DEVICE Filed Nov. 26, 1927 HIS - in; machine.

I i 'iew f Fig. 4 being' -onthe li 4;4 of

Patented Mar. 4, 1 930 sum- 3.. BROWN,

OF BURLINGAME, CALIFORNIA, ASSIGNOR OF ONE-HALF TOJ'OSEIPH ,4. BROWN, OF SAN, FRANCISCO, CALIFORNIA I SAFETY DEVICE Application fil ed November 26, 1927. Serial No. 235,825.

I invention relates to guards forjma chines having working'parts liable to cause injury and particularly to guards iorband' saws.

" Itfis an object ofmy invention to provide a) guard which will automatically become operativewhen the machine to which it is at- V tached has been disconnectedfrom its power supply and is coasting, and the operator o therefor hasunconsciously relaxed his vigilance Another object of my invention is to "provide aguard which is operative until delibj .erately adeinactive by'the operator ofthe Still another object is to provide a guard which mayreadily be applied to machines of various: makes, and which may be installed on, amachine after it is-in service. "2o 1 ;My inventionjpossesses other ob ects and valuable-features, some iofwhich will be set forth in the following description of my invention which isillustrated in the drawingsforining part of thespecification. It is i z'fi to be understood, that I do not limit myself to theshowing made; by thejsai'd description and drawings,as I may adopt varying forms ofiniy invention withinthe scope of the Y claims. Y f

.Referrin'gto thedrawings; M t Fig. l isfa front" elevation of aband sawing machine having tlie'guard of my inven- .tion installed thereon- The figure shows schematically thepower circuit of the machine, and the dotted lines show the actlve positionof the guard- 2 isa side elevation the machine 7 shownin Fig, Partsof, the machine are l cut away in both figuresto' conserve space.

.Fig. ,3 is a detail-"sectional view on an enlarged scale,the plane ofsec'tion'be ng on theline 3 3 'iOf1Fig. 1..

'- enlarged scale, lshowing tlie pole, construction of thefmagnetic jclutch; the plane of Fig.4 and 5"arefld etail views, {also on an I Fig. ;,.and. of ,F i-g.f5 being a section on the li es-"5 Fig.;4..; I

tact withthein. Thisis especially true of woodworking machinery as a class. The cut- UNITED'LSTATES PATENT OFFICE ters work at high speed, the moving parts are heavy, and the friction is low. Such machines are dangerous at all times, but GX 'perience shows that a large proportion of the injuries resulting from their use occur after the power supply is turned off, and while the machine is running under its momentum, or coasting.

There are two causes for this state of affairs. The firstis that when the machine is running at full speed it makes a sound which serves as an audible warning signal, and attracts attention to the fact that it is running. As the machine slows down this sound drops in both volume and pitch, and becomes inaudible when the machine still has momentum enough toinflict serious harm. The second cause is an unconscious let down of vigilance on the part of the operator after he has shut 'oif the power. subconsciously he regards the danger as past, because he has taken the necessary steps to remove it, and

inthe few seconds or minutes before it acventscontact withthe dangerous parts at all times such a guard should be used, but there is a'class'of ma'chines such as band-saws where a guard of'this characterwould prevent the'satisfactory operation of themachine, and it is to meet this situation tha my invention finds its application.

In terms of broad inclusion, my invention comprises a guard whichnorm'ally assumes its'operativ'e position, either thru the action I of gravity, a spring, or other means. The guard may be moved from this position by the operator, and a clutch holds the guard in the inoperative position as long as power is being appliedto the machine. Interrupting the power supply releases the clutch,'and the guard then immediatelyreturns to its operative or effective position, remaining in this position until the 'powersupply is re-established and the guard is again moved by the operator. g

Describing a preferred form of my invenries an arm 8 extending overthe table. A

vertical guideway 9 rising from the arm has a sliding block 11 mounted thereon, adjust- These brackets carry able by the hand-wheel 12. On the block is journaled the pulley 13 over which runs the saw 14. e The arm 8 extends past the guideway and in-its ends is a square verticalhole thru which slides the saw guide 16 which may be locked imposition by the knuckled screw 17. At the lower end of the saw guide is formed a foot a on which are mounted a pair of rollers 18 hetween which the saw runs, and a rotatahle disk 19 a ainst which the back edge of the saw abuts. K trough shaped guard 21 prevents accidental contact with the back reach of the saw.

To this machine my guard is applied; A pair of horizontal brackets'22 are fastened to the end of the arm 8 by the cap-screws 23. an upright rectangular bar24. c

The lower end of the bar 24 extends a few inches below the arm 8, dropping as low as possible Without interfering with the foot of the guide 16. The upper end of the bar extends above the highest position of the axis of the pulley 18 about as far as the lower end is above the table. These distances are approximate only, as the exact dimensions are not important. I I 1 Near its lower end the bar carries a bolt 26 The bolt has a T or mushroom head, and

' a shoulder which restsagainstthe bar; T0-

gether, with a similar bolt 27 carried bythe upper portion of the bar it serves as.a sup-' port and guide on which the guard slides. At thetop of the bar is mounted an electro magnet. The magnet ispreferably protected by a cup shaped metal housing, riveted to the top ofthe bar. The magnet itselfma'y be of the familiar horse-shoe form, secured within the housing with its poles pointing down.

The construction of the magnet will vary with the type of: motor and currentsupply available for driving the saw. Where the supply is direct current the core 29 carries acoil 31 consistingof aifew turns of wire, and is connected in se rieswith the motor 32 as shown of the supply current, 1 L h For the guard 'tselfI prefer to use a metal schematically in Fig. 1. If the current supplyis alternating the preferred connection is in shunt with, the motor. In this case a large number of turns is used for the coil, and a shading coil 3.3 may be used in the well known manner, surrounding a portion of the pole faces in order to obtain a continuous traction from the magnet in spite of the di'scon tinuous nature of the current, I prefer to use a laminated eorewhateverthe character angle34. One web of the angle is slotted at its upper and lower ends. The bolts 26 and 27 pass thru these slots and the guard slides V I on them, the proportions being such that in its raised position the bottom of the guard is level with the bottom of the bar, while in its lower position the guard rests on thetable7. Atits upper end the guard carries a hori- Zontally extending armature 36 which en gages with the magnet poles when the guard v is raised. A rubber bumper 37 is preferably fixed atthe bottom of the guard to absorb the shock When it'is dropped, a handle 38 near the bottom of the guard facilitates raising it.

The mode of operation of the device is evident. WJhen themotor is started the magnet the armature 36 engages with the magnet it willbe held there,allowingthe saw to be used i in the usual manner, without interference from the guard. .Turning oif the motorv deener izes thema net. andithe uard at once t) D I 5 drops, is coasting.

Altho the V scribed offers perhaps the readiest means of giving full "protectionwhile the saw electro-ma'gnetic1 control de-' operation, it is possibleto obtain'the same protection bymechani'cal means, a catch in-' working parts'liable" to causeinjury, means for driving said parts-,a movable'guard for said driving means'for retaining said guard in inoperative position-l 2'. In combination with'a machine 'having working parts' liable" to ausein ury, means for drivlngsaid parts, a movablefguard for working partsliable to causeinjury, means movable to airinoperative position, and

means 5 controlled by said driving means for' retainlng said guard n. said poeit1onduring" operation of said driving means. 1

for driving said parts, alguar'dfmanua-lly- 4. In combination with a machine having working parts liable to caus'e injury, an elec tric driving motor, a supply oircuitffor'said' motor, a movable guard for said workin parts, and an electro-magneticfclutch actu ated from said supply circuit for retaining said guard ininoperativeiposition when said supply clrcu t s energized. Y

g 5., In combination'with 7 working parts liable' to causeinjury, a'nelec v trio driving, motor, a supply circuitfor said c. i2 5 machinehavlng motor, a movable guardffor saidworking parts,:an electroemagnet on said machine'a i. Y is excited. If the guard 1s then raised until 7 said working parts, and means controlled by tuated from said supply circuit and an armature on said, guard cooperating with said magnet to hold the guard in inoperative position when the magnet is energized. I

6. In combination with a band saw, a frame for said saw, an electric motor for driving said savv, a supply circuit for said motor, a guard for said saw movable on said frame and electro-magnetic means actuatedfrom said supply circuit for retaining said guard energized.

in inoperative position when said circuit is 7. In"c0mbination with a band saw, a frame for said saw, an electric motorrfor driving said saw, a supply circuit for said motor, a guard for said saw vertically slidable A on said frame, and electro-magnet means actuatedfrom said supply circuit for retaining' said guard in its upper position.

In testimony whereof, I have hereunto set r my hand.

SAM ,R." BROWN. 

